These settings control the type of Motorola 68000 CPU which will be emulated.
CPU Type:
68000 is the basic CPU type, as found in the Amiga 500, 1000, and 2000 models.
68010 is a slightly more advanced 68K member, but never actually shipped in a real Amiga.
68020 is a much more advanced 68K CPU, with some new instructions, and a fully 32-bit engine. Used in the A2500 for brief period on the A2520 card.
68EC020 is the same as a 68020 CPU, but with only 24 address-lines. This is the CPU used in the Amiga 1200 model, and does not allow for any Zorro-III expansion cards in the system. Because WinUAE uses virtual Zorro-III expansion cards to provide Picasso96 RTG support, no Picasso96 support is possible with this CPU type.
68EC020/68881 is similar to the above CPU type, but adds a dedicated Floating Point Unit (FPU) for faster math operations.
68020/68881 is the most powerful combination that WinUAE can emulate, as found in the A2500 computer.
CPU Emulation Speed:
Fastest possible lets the CPU section of the emulation run as many cycles as possible, while still maintaining emulation of the custom-chips at the appropriate rate. It is important to keep sound and graphics synchronized, no matter how fast the PC is.
Approximate A500 speed limits the CPU emulation to run the same number of cycles per vertical-blank as a standard A500 would. In other words, for every 50Hz refresh of the graphics, the same number of CPU instructions will be executed as on a real A500 computer.
Adjustable between CPU and chipset lets you tweak the balance of power between custom-chip emulation, and CPU speed. Some games and demos require this setting to be adjusted. This setting is the only CPU setting which can be changed once WinUAE is running.
Slow but more compatible is only available when the CPU type is a 68000. Some games and demos require this setting for proper compatibility.